CBN Abrasives Research Articles

Investigation of Manufacturing Technology in Electroplating CBN on Gear-Honing-Tool

In the paper, a new technology combining conventional CBN electroplating and thermal diffusion in vacuum to produce gear-honing-tool for hardened tooth is introduced. The two factors, such as planting CBN abrasives and combination between electroplating layer and matrix that can affect the quality of gear-honing-tool, are investigated. Experiments show that using suspension CBN abrasive electroplating combined with thermal diffusion in vacuum can ensure the quality of planting CBN abrasives of gear-honing-tool and obtain the semi-metallurgy binding layer between CBN abrasives and matrix that withstands the force of honing gears.

Development of Vitrified Bond CBN Wheel for Internal Precision Grinding of the Air-Conditioner Compressor Piston Hole

Manufacturing of vitrified bond CBN wheels for internal precision grinding of the air-conditioner compressor piston hole is still big challenge to all of the domestic manufacturers. Recently, by choosing pre-melting mixed CBN abrasives and a proper sintering process, a cost-effective method was conceived to produce grinding wheels of comparative quality. The grinding performance of wheels was evaluated with a series of internal precision grinding of compressor piston hole. Experimental results show that the vitrified bond CBN grinding wheel produced by this method has better grinding performance, and can be substitute to the same type of grinding wheels imported. But the manufacturing cost is only 60% of the wheel imported according to estimation.

Profile Grinding of Superalloys with Ultrafine-Crystalline cBN Wheels

This paper deals with the grinding characteristics of newly developed polycrystalline cBN (cBN-U) abrasives in creep feed profile grinding of nickel-based superalloys. Experiments for producing a V-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using the new polycrystalline cBN-U and representative conventional cBN (cBN-B) grits. When grinding with cBN-U abrasives, both radial wear and profile wear are less, and hence the grinding ratio is around 10 times higher than that with the conventional cBN-B abrasives. Grinding forces in grinding with cBN-U abrasives are reduced by 20-30% compared with those in Grinding with cBN-B abrasives. The cBN-U abrasive is suitable for the applications with a high dimensional accuracy in creep feed profile grinding for nickel-based superalloys, because it gives less profile wear, and hence better form retention, than conventional cBN abrasive.

Ultra-low Pressure Super-finishing to Produce Nano-surfaces(Surface and edge finishing)

We have developed a new ultra-low pressure method for obtaining a finer finish in super-finishing using vitrified bonded cubic boron nitride (cBN) abrasive stones, recommended for use in the burnishing stage. This is a finer finish with very small or no stock removal, than ordinarily occurs in a conventional process using aluminum oxide or silicon carbide stones. We have fabricated a prototype super-finishing machine that provides stable ultra-low pressures using an air slider. Super-finishing was attempted using ultra-low pressures (less than 0.1MPa) with cBN abrasives averaging less than 8μm in diameter. As a result, super-finishing with a processing pressure of 0.02MPa could be achieved using fine-grit cBN. The study demonstrated that it is possible to obtain a surface finish on the nano-order under ultra-low pressure conditions.

Evaluation of grinding fluids in the grinding of a martensitic valve steel with CBN and alumina abrasives

In this paper the performances of different cutting fluids and grinding wheel types were analysed in the grinding of SAE HVN-3 workpieces. The resulting residual stress, wheel wear and roughness were evaluated. The influence of the cutting fluid jet velocity vj was also analysed. As a conclusion, the lubrication ability seems to be the governing factor in the cutting fluid performance. The use of CBN wheels can significantly reduce the thermal damage in grinding, leading to compressive residual stresses. The CBN wheel and the cutting oil give an optimum combination for performing this grinding operation.

Friability and crushing strength of micrometer-size diamond abrasives used in microgrinding of optical glass

In abrasive grinding, the properties of the abrasives and their response to impact loading play a significant role in determining the results achievable. For micrometer-size diamond abrasives used for bound-abrasive microgrinding of optical glass, friability testing is used to estimate the related particle properties. Friability and crushing strength of diamond abrasives are estimated based on the data from comminution of sample powders on a commercial SPEX mixer/mill. Different diamond abrasives as well as a CBN abrasive are tested. Evolution of powder size and size distribution with comminution time is characterized with a HORIBA laser scattering analyzer. Correlation is established for the impact stress and the probability of fracture during comminution. This study demonstrates how to combine the ease of data acquisition found in a conventional friability test with the capability of predicting specific mechanical properties normally found only by crushing individual abrasive particles.

Grinding Characteristics of Polycrystalline CBN Abrasive Grits Having an Ultrafine Crystal Structure.

A new type of polycrystalline CBN grit has been developed by direct transformation at high temperature and pressure from hBN of high purity which was produced using a chemical vapour deposition process. This new polycrystalline CBN (N-CBN) grit possesses an average primary crystal grain diameter less than 1 μm and its fracture strength is around 1.5 times higher than conventional polycrystalline CBN (P-CBN) grit. In grinding high-speed tool steel, the grinding ratio of the wheel containing N-CBN grits is 7∼9 times higher than that of the wheel containing P-CBN grits. The estimated tool life of the N-CBN wheel, based on the roughness of the finished surface, is 1 much longer than that of the P-CBN wheel.

レジンボンドCBN砥石の目直しに関する研究 (第3報)

This paper deals with the relation between the properties of the wheel surface and the surface roughness of the workpiece for various truing and dressing conditions. In addition, the availability of the stick-aided loose abrasive dressing method, in which the loose abrasives are added to the ordinal WA stick method, is discussed. The stick-aided loose abrasive method can form the chip pocket effectively without much damage of CBN abrasives. Cutting edge distribution on the working surface of the wheel can be controlled by a series of dressing/truing operations over a wide range. Good finished surface is obtained as the accumulative cutting edge increases in a certain extent. An excessive re-truing makes the cutting edge too flat, so that a loading of welding type occurs in grinding and a good finished surface is unobtainable under such conditions. Loading increases with soluble type grinding fluids, especially in water-rich dilution and decreases with oil-based grinding fluids in grinding.